The present invention is directed to related apparatus systems, equipment and methods for beating heart bypass surgery.
Major heart surgery has been accomplished by procedures that require full cardiopulmonary bypass (CPB), and complete cessation of cardiopulmonary activity. Open heart surgery typically requires significant hospitalization and recuperation time for the patient. The average mortality rate with this type of procedure is low, but is associated with a complication rate that is often much higher. While very effective in many cases, the use of open heart surgery to perform various surgical procedures such as coronary artery bypass grafting (CABG) is highly traumatic to the patient. These procedures require immediate postoperative care in an intensive care unit, a period of hospitalization for at least several days, and an extended recovery period. In addition, open heart procedures require the use of CPB which continues to represent a major assault on a host of body systems. For example, there is noticeable degradation of mental faculties following such surgeries in a significant percentage of CABG patients. This degradation is commonly attributed to cerebral arterial blockage and emboli from debris in the blood generated by the use of CPB during the surgical procedure. At the same time, the dramatic increase in the life expectancy of the general population has resulted in patients that are more likely to be older and in poor health, with less cardiovascular, systemic, and neurologic reserve needed to recover from the trauma caused by the use of CPB. As a consequence, inflammatory, hemostatic, endocrinologic, and neurologic stresses are tolerated to a much lesser degree by a significant number of patients today, and play a more significant role in CPB-induced morbidity.
The CABG procedure generally involves open chest surgical techniques to treat diseased vessels. During this procedure, the sternum of the patient is cut in order to spread the chest apart and provide access to the heart. During surgery the heart is stopped, and by the use of CPB blood is diverted from the lungs to an artificial oxygenator. In general, a source of arterial blood is then connected to a coronary artery downstream from the occlusion. The source of blood is often an internal artery, and the target coronary artery is typically among the anterior or posterior arteries which may be narrowed or occluded.
The combined statistics of postoperative morbidity and mortality continue to illustrate the shortcomings of CPB. The extracorporeal shunting and artificially induced oxygenation of blood activates a system wide roster of plasma proteins and blood components in the body including those that were designed to act locally in response to infection or injury. When these potent actors are disseminated throughout the body without normal regulatory controls, the entire body becomes a virtual battleground. The adverse hemostatic consequences of CPB also include prolonged and potentially excessive bleeding. CPB-induced platelet activation, adhesion, and aggregation also contribute to a depletion in platelet number, and is further compounded by the reversibly depressed functioning of platelets remaining in circulation. The coagulation and fibrinolytic systems both contribute to hemostatic disturbances during and following CPB. However, the leading cause of morbidity and disability following cardiac surgery is cerebral complications. Gaseous and solid micro and macro emboli, and less often perioperative cerebral hypoperfusion, produce neurologic effects ranging from subtle neuropsychologic deficits to fatal stroke. Advances in computed tomography, magnetic resonance imaging, ultrasound, and other imaging and diagnostic techniques have added to the understanding of these complications. But with the possible exception of perioperative electroencephalography, these technologies do not yet permit real time surgical adjustments that are capable of preventing emboli or strokes in the making. Doppler and ultrasound evaluation of the carotid artery and ascending aorta, and other diagnostic measures, can help identify surgical patients at elevated risk for stroke and are among the growing list of pharmacologic and procedural measures for reducing that risk.
CPB also affects various endocrine systems, including the thyroid gland, adrenal medulla and cortex, pituitary gland, pancreas, and parathyroid gland. These systems are markedly affected not only by inflammatory processes, but also by physical and biochemical stresses imposed by extracorporeal perfusion. Most notably, CPB is now clearly understood to induce euthyroid-sick syndrome which is marked by profoundly depressed triiodothyronine levels persisting for days following cardiothoracic surgery. The efficacy of hormone replacement regimens to counteract this effect are currently undergoing clinical investigation. By contrast, levels of the stress hormones epinephrine, norepinephrine, and cortisol are markedly elevated during and following CPB, and hyperglycemia is also possible.
Alternatives to CPB are limited to a few commercially available devices that may further required major surgery for their placement and operation such as a sternotomy or multiple anastomoses to vessels or heart chambers. For example, some present day devices used in CPB may require a sternotomy and an anastomosis to the ascending aorta for placement. The main drawbacks of these devices include their limited circulatory capacity, which may not totally support patient requirements, and their limited application for only certain regions of the heart, such as a left ventricular assist device. Other available devices that permit percutaneous access to the heart similarly have disadvantages, such as their limited circulatory capabilities due to the strict size constraints for their positioning even within major blood vessels. Moreover, the relative miniaturization of these types of devices present a high likelihood of mechanical failure. In further attempts to reduce the physical dimensions for cardiac circulatory apparatus, the flow capacity of these devices is significantly diminished.
During cardiac surgery, the heart is either beating, in which case the heart continues to circulate the blood through the lungs to maintain the patient, or immobilized entirely in which case oxygenation and circulation of blood to maintain the patient requires use of CPB. Bypass surgery on a beating heart has been limited to only a small percentage of patients requiring the surgical bypass of an occluded anterior heart vessel. These patients typically could not be placed on CPB and were operated on while the heart was kept beating. Meanwhile, patients requiring surgery on posterior or lateral heart vessels and whose hearts must be immobilized and placed on CPB often suffer major side effects as previously described.
The medical community is currently performing more beating heart bypass surgery in an effort to avoid the use of artificial heart-lung machines. The need for apparatus systems, methods and associated equipment to enhance the capability and versatility of beating heart surgery, is ever increasing. The current trend toward thoracoscopic methods of performing bypass surgery, without opening the chest cavity, have resulted in limited success and applicability primarily due to the limited number of heart vessels which can be accessed through thorascopic methods. A major limitation of thorascopic bypass surgery methods is due to the fact that only the anterior heart vessels are accessible for surgery. More importantly, even open chest surgery providing full access to the heart also requires CPB when bypass surgery is performed on the lateral or posterior vessels of the heart, due to the fact that the heart must be stopped when it is moved from its normal position and manipulated for surgical access to the various heart vessels.
The present invention provides apparatus systems and methods which enable beating heart surgery on all vessels of the heart, but especially the lateral and posterior vessels of the heart, which have been effectively inaccessible for beating heart bypass surgery. The systems and methods of this invention enable such beating heart bypass surgery by providing apparatus for protecting the right side from collapse or other restriction, such as ineffective pumping due to heart muscle stress or compression, in order to maintain at least partial pulmonary blood flow through the beating heart, apparatus for augmenting or supplementing the pulmonary blood flow with a blood pump/cannulation system having a minimum priming volume and apparatus for supporting the beating heart in a lifted or manipulated position for bypass surgical access to heart vessels. When desired, the systems and methods of this invention can optionally include apparatus for protecting the left side from collapse to maintain at least partial aortic blood flow through the beating heart and apparatus for supplementing or augmenting the aortic blood flow with a blood pump system having a minimum priming volume. However, in some instances, the aortic blood flow through the left side of the heart can be sufficiently maintained during beating heart surgery without protecting the left side or supplementing or augmenting the aortic blood flow through the beating heart. In reference to this invention, xe2x80x9cright sidexe2x80x9d refers to and includes the vena cava veins, the right atrium, the right ventricle, the pulmonary artery and any combination or all thereof. Similarly, xe2x80x9cleft sidexe2x80x9d refers to and includes the pulmonary veins, the left atrium, the left ventricle, the aorta and any combination or all thereof. Also, as used herein vena cava includes superior and inferior vena cava, pulmonary artery and vein includes branches thereof and aorta includes the aortic vessels which are near the heart and exposed during open chest bypass surgery.
A major obstacle to performing beating heart bypass surgery on lateral or posterior heart vessels is that when the beating heart is lifted or manipulated to provide surgical access to the lateral or posterior heart vessels, the right side, i.e., the right atrium, or the right ventricle, or both, tends to collapse or diminish in pumping capacity to an unacceptably low level and/or the pulmonary artery tends to collapse, kink or become otherwise unduly constricted while the heart is displaced. This invention provides apparatus systems and methods for protecting the right side and for maintaining blood flow through the right side while the beating heart is lifted and manipulated for full surgical access to lateral and posterior heart vessels, thus enabling unrestricted beating heart bypass surgery.
In one aspect, this invention provides a system for preventing collapse of the vena cava, right atrium, right ventricle and/or pulmonary artery during beating heart bypass surgery comprising a pump and cannula system wherein the cannula portion is adapted for insertion through the tricuspid valve, through the pulmonary valve and a sufficient length into the pulmonary artery to prevent collapse of the right atrium, right ventricle and/or pulmonary artery and to maintain at best partial blood flow therethrough by the beating heart pumping action while the beating heart is lifted or displaced during surgery. Access for insertion of the cannula portion can be through the vena cava, e.g., from a femoral vein incision, through an incision in the wall of the vena cava or in the wall of the right atrium. If the cannula is not inserted through the tricuspid valve, but only through the pulmonary valve and into the pulmonary artery, access could be through an incision in the wall of the right ventricle or reverse access can be used by entering through an incision in the wall of the pulmonary artery. Separate cannulas can be employed, i.e., one introduced through the right atrium and through the tricuspid valve but ending in the right ventricle, and a second introduced by any desired access and beginning in the right ventricle and extending through the pulmonary valve and a desired length, according to this invention, into the pulmonary artery. The pump portion of the system is adapted for intake of blood upstream of the pulmonary valve or upstream of the tricuspid valve and output of blood into the right ventricle or the pulmonary artery while the beating heart is displaced during surgery. The pump system is preferably integral with the above cannula or cannulas, particularly in a concentric double wall cannula configuration, or can comprise pump cannulas separate from and in addition to the above cannulas which protect the right side from collapse. The cradle system is adapted for supporting the beating heart while the heart is displaced and for providing surgical access to lateral or posterior heart vessels.
In another aspect, this invention further provides an optional embodiment which, in addition to the above system for the right side, a separate pump and cannula system is provided for the left side wherein the cannula portion is adapted for insertion through the bicuspid valve, through the aortic valve and a sufficient length into the aorta to prevent collapse of the pulmonary vein, left atrium, left ventricle and/or aorta and to maintain blood flow therethrough by the beating heart pumping action while the beating heart is lifted or displaced during surgery. As indicated above for the right side, access for the left side cannula or cannulas can be from any desired upstream or downstream incision. One or two cannulas may be employed for preventing collapse of the left side and the pump portion of the system, which may have its separate cannulas, is adapted for intake of blood upstream of the aortic valve or the bicuspid valve and output of blood into the left ventricle or the aorta while the heart is displaced during beating heart surgery.
As is apparent, either the right side system or the left side system or both may be used for a particular patient or procedure. Whether the cannula for pump output extends into the pulmonary artery/aorta or extends only into the respective ventricle will similarly depend on the requirements for a particular patient or procedure. In some instances the beating heart blood flow is impeded due to partial compression, wrinkling or other distortion of the ventricle muscle. While the muscle is working, it is unable to both fill the ventricle with blood and expel or pump the blood in sufficient quantity. The pump system of this invention can be used by positioning the pump cannula output end in the ventricle to fill or preload the ventricle with blood, so the heart muscle can then pump or expel the blood from the ventricle, even though the muscle is not in its normal shape or position. In this aspect of the invention, beating heart blood flow can be maintained while the heart is displaced during surgery without the necessity of the cannula extending through the pulmonary/aortic valve.
In another aspect, this invention provides a pump and cannula system for use in beating heart bypass surgery wherein the pump and its cannula system have a priming volume less than about 1,000 ml. In one embodiment of this aspect the pump and cannula system comprises concentric intake and output conduits adapted for insertion into a single incision. In another embodiment of this aspect of the invention, the pump and cannula system comprise an intake cannula for insertion in the upstream vessel or heart chamber and an output cannula for insertion downstream into the pulmonary artery or the aorta. In a further embodiment of this aspect the pump and cannula system comprises a miniaturized pump having a sterile drive motor suitable for placement of the pump including the drive motor close to or even within the chest cavity during the beating heart bypass surgery. In a further embodiment of this aspect a preferred pump is a reverse flow pump having a minimum priming volume, but a cable driven axial flow pump or other conventional blood pump can be used in this invention.
In another aspect, this invention provides a cannula system for protecting selected portions or all of the right side from collapse during beating heart surgery, an optional cannula system for protecting selected portions or all of the left side from collapse and optional pump and cannula systems for use with the right and/or left side protection cannulas. In some patients all that may be required is the protection cannula or cannulas in the right side to allow the beating heart to maintain sufficient pulmonary blood flow during the beating heart bypass surgery and it may not be necessary to use the pump system to provide supplemental pulmonary blood flow and may not be necessary to protect the left side or to provide supplemental arterial blood flow. For such patients, this invention enables beating heart bypass surgery without artificial pumping of the blood and with minimum invasive apparatus. In some patients, beating heart bypass surgery can be started or attempted with only right side protection cannula(s) in place, then right side supplemental pumping of pulmonary blood flow added during the bypass surgery (or even after the surgery) by separately inserting the pump system according to this invention. Likewise, left side protection cannula(s) and/or left side supplemental pumping of arterial blood can be added as needed during (or after) the bypass surgery by insertion of the cannula(s) and/or pump systems according to this invention. Thus, this invention provides optional incremental apparatus that may be used only according to particular patient needs in order to minimize the invasiveness of the bypass surgery procedure.
In another aspect, this invention provides a valved cannula having an outside diameter adapted for positioning in the right ventricle through the pulmonary valve and in the pulmonary artery, having blood inlet in the ventricle portion, a blood outlet in the artery portion, a one-way valve or check valve between the inlet and outlet adapted to allow blood flow substantially only in one direction from the inlet toward the outlet and a positioning lead attached to the cannula for holding the cannula in proper position in the heart and the pulmonary artery. This pulmonary valve cannula is adapted to receive blood through the inlet from the right ventricle when the right ventricle contracts and expel the blood through the outlet in the pulmonary artery. The one-way valve is adapted to prevent significant back flow of blood through the cannula back into the right ventricle. The cannula may be adapted and sized to allow blood to flow between the pulmonary valve and the external surface of the cannula when the right ventricle contracts and to allow the pulmonary valve to substantially seal to the external surface of the cannula and prevent significant back flow of blood around the cannula back into the right ventricle, when the right ventricle expands. The portion of the cannula contacting the pulmonary valve can be a different outside diameter than the ventricle portion or the artery portion of the cannula, or both. It may be desirable in some patients to have the outside diameter of the cannula at the pulmonary valve contact portion smaller to allow the maximum beating heart blood flow around the outside of the cannula when the pulmonary valve opens. In other patients it may be desirable to have a larger diameter to maximize the beating heart blood flow through the cannula as opposed to around the cannula. The inlet and outlet can be conventional blood cannula configurations and/or can comprise orifices, slits or other openings at desired locations and intervals along portions of the length of the cannula. The ends or openings can comprise baskets, cages or other guards to prevent suction of heart tissue or blood vessel wall into the cannula. The internal valve in the cannula can be any suitable one-way or check valve, such as a flap valve, slide valve, spring loaded circular valve or ball valve, membrane valve, duck bill valve or other design and can be any material appropriate for a blood flow valve. The positioning lead can be attached to the cannula in any desired way and any desired location and adapted for holding the cannula in position during use. The lead can also be useful in inserting and guiding the cannula through the appropriate vessel incision into proper position. The cannula can be inserted with a guide wire/balloon arrangement from an upstream incision.
In another aspect, this invention provides a valved cannula having an outside diameter adapted for positioning in the right atrium through the tricuspid valve and in the right ventricle, having a blood inlet in the atrium portion, a blood outlet in the ventricle portion, a one-way valve or check valve between the inlet and outlet adapted to allow blood flow substantially only in one direction from the inlet toward the outlet and a positioning lead attached to the cannula for holding the cannula in proper position in the heart. This tricuspid valve cannula is adapted to receive blood through the inlet from the right atrium and expel the blood through the outlet in the right ventricle when the right ventricle expands. The one-way valve is adapted to prevent significant back flow of blood through the cannula back into the right atrium when the right ventricle contracts. The cannula is preferably adapted and sized to allow blood to flow between the tricuspid valve and the external surface of the cannula when the right ventricle expands and to allow the tricuspid valve to substantially seal to the external surface of the cannula and prevent significant back flow of blood around the cannula back into the right ventricle when the right ventricle contracts. The portion of the cannula contacting the tricuspid valve can be a different outside diameter than the atrium portion or the ventricle portion of the cannula, or both. It may be desirable in some patients to have the outside diameter of the cannula at the tricuspid valve contact portion smaller to allow the maximum beating heart blood flow around the outside of the cannula when the tricuspid valve opens. In other patients it may be desirable to have a larger diameter to maximize the beating heart blood flow through the cannula as opposed to around the cannula. The inlet and outlet can be conventional blood cannula configuration and/or can comprise orifices, slits or other openings at desired locations and intervals along portions of the length of the cannula basket or cage to prevent heart tissue suction. The ends or openings can comprise baskets, cages or other guards to prevent suction of heart tissue or blood vessel wall into the cannula. The internal valve in the cannula can be any suitable one-way or check valve, such as a flap valve, slide valve, spring loaded circular valve or ball valve, membrane valve, duck bill valve or other design and can be any material appropriate to a blood flow valve. The positioning lead can be attached to the cannula in any desired way and any desired location and adapted for holding the cannula in position during use. The lead can also be useful in inserting and guiding the cannula through the appropriate vessel incision into proper position. The cannula can be inserted with a guide wire/balloon arrangement from an upstream incision.
In another aspect of this invention, the above pulmonary valve cannula and the above tricuspid valve cannula may be combined or formed as a single cannula adapted to the position through both the tricuspid and pulmonary valves with the respective check valves, inlets and outlets properly positioned according to the functions set forth above for each. The advantages of this single cannula configuration include single incision, single guide wire and single positioning lead.
In another aspect, this invention provides apparatus for supporting and preventing collapse of the kink zone in the pulmonary artery. In addition to apparatus for supporting and preventing collapse of the right atrium and right ventricle, this invention provides a separately adapted stent to prevent collapse or kinking of the pulmonary artery to maintain blood flow through the pulmonary artery and/or through the stent during beating heart bypass surgery. When the beating heart is lifted and manipulated for surgical access to the posterior or lateral blood vessels, the pulmonary artery tends to fold or kink and restrict or stop the beating heart blood flow. As used herein the pulmonary artery xe2x80x9ckink zonexe2x80x9d is the portion of the pulmonary artery between the heart and the lungs where the artery tends to fold, kink or restrict when the beating heart is lifted or manipulated for surgical access to the lateral or posterior heart vessels. This kink zone is usually in the portion of the pulmonary artery within about 15 cm from the heart. In this aspect of the invention, the pulmonary artery stent is adapted to have diameter and length appropriate to extend the length of the kink zone and an appropriate distance on either side of the kink zone to assure full protection of the pulmonary artery during a beating heart surgical procedure. The pulmonary artery stent also comprises a handle for inserting and withdrawing the stent through an appropriate incision. Typically the stent will further comprise a guide wire/balloon for placement of the stent in the proper position in the pulmonary artery. In some patients the pulmonary artery stent may be all that is required to protect the left side during a particular beating heart surgical procedure. In other instances the beating heart surgery may require only the pulmonary artery stent and the above tricuspid valve cannula. In other instances, the use of a pump and cannula system described above may be needed to supplement or augment the right side flow of blood produced by the beating heart during bypass surgery.
This invention further provides the above stent adapted for positioning in other portions of the right side to prevent collapse or restriction in a similar xe2x80x9ckink zonexe2x80x9d in the vena cava veins, right atrium or right ventricle and to maintain pulmonary blood flow through the right side while the heart is displaced and manipulated during beating heart bypass surgery. As is apparent, the above stent may also be adapted for positioning in the aorta, pulmonary veins, left atrium and/or left ventricle to maintain aortic beating heart blood flow during beating heart bypass surgery.
As is apparent, this invention enables the use of various combinations of the above aspects of this invention to meet the requirements of a particular patient for the successful performance of beating heart surgery. Selective use of the above stents, cannulas and/or pump and cannula systems in their various configurations results in minimum invasiveness and minimum contact of the blood with apparatus in or outside the body during beating heart bypass surgery. Thus, this invention provides apparatus systems to enable beating heart bypass surgery ranging from one or more stents placed to prevent restriction of blood flow produced by the beating heart to pump and cannula systems placed through the entire right side and entire left side to both protect the beating heart blood flow and to augment, supplement or, when necessary, temporarily replace the beating heart blood flow during the bypass surgery.
In preferred embodiments of this invention, the cradle for supporting the beating heart during beating heart bypass surgery can be a flexible film or mesh, or it can be a rigid or semi-rigid member with appropriate openings. The cradle not only provides support for the beating heart in the desired and necessary position for surgical access to heart vessels, it also provides visual access to the appropriate heart vessels on which the bypass surgery is performed.
In another aspect, this invention provides a method for performing beating heart bypass surgery which comprises:
inserting the cannula portion of a pump and cannula system through the tricuspid valve, through the pulmonary valve and a sufficient length into the pulmonary artery to prevent collapse of the right atrium, right ventricle or pulmonary artery when the heart is lifted or displaced during surgery;
pumping blood from upstream of the pulmonary valve into the pulmonary artery to augment the flow of blood through the pulmonary valve produced by the beating heart; and
supporting the beating heart in a cradle to provide surgical access to the lateral or posterior heart vessels.
In another embodiment of this invention, the system for preventing collapse of the right atrium, right ventricle or pulmonary artery and maintaining blood flow across the pulmonary valve during beating heart bypass surgery comprising:
a cannula adapted for insertion through the tricuspid valve, through the pulmonary valve and a sufficient length into the pulmonary artery to prevent collapse of the right atrium, right ventricle or pulmonary artery while the beating heart is lifted or displaced during surgery;
a pump system adapted for removing blood from the vena cava or the right atrium and transporting the blood through a cannula and into the pulmonary artery; and
a cradle for supporting the beating heart while the heart is displaced during surgery and for providing surgical access to lateral or posterior heart vessels.
In another aspect, this invention provides a method for performing beating heart bypass surgery which comprises:
inserting a cannula through the tricuspid valve, through the pulmonary valve and a sufficient length into the pulmonary artery to prevent collapse of the right atrium, right ventricle or pulmonary artery when the heart is lifted or displaced during surgery;
connecting a pump intake tube through an incision in the wall of the right atrium to remove blood from the right atrium;
connecting the pump outflow tube into the pulmonary artery through an incision in the wall of the pulmonary artery;
pumping blood from the right atrium through the pump into the pulmonary artery; and
supporting the beating heart in a cradle during surgery for surgical access to the heart vessels.
As is apparent, this invention provides and enables various embodiments of methods for beating heart bypass surgery utilizing the various selected combinations of the above described stents, cannulas and pump and cannula systems as appropriate for a particular patient or procedure following the disclosures of this invention.